The present invention relates to a roofing structure, for example for making a generally transparent or translucent vault for covering a defined zone.
The structure according to the invention makes it possible, particularly but not exclusively, to make portions of transparent or translucent surfaces in the roof of a building, the roofing of corridors, passages, shelters, porches, etc.
Structures of this type are generally constituted by a plurality of transparent or translucent plates, for example made of plastics material, fixed by being gripped between hoop elements and possibly crosspieces which define its frame.
Such structures must comply with criteria of tightness, aesthetics, ease of assembly and occasionally ease of modification of the structure, for example by adding other surface levels thereto whilst using the structure which has already been positioned. Furthermore, they generally use materials of different natures which, in particular, present different coefficients of expansion. When the structure is made, it is therefore necessary to take into account the differences in expansion in the materials assembled together.
Presently existing structures are described, for example, in U.S. Pat. Nos. 2,842,073, 3,307,309, 3,325,951, 3,473,276, 3,434,250 and 3,762,120. Some of these structures are constituted by plates of which the transverse edges are housed between superposed curved sections constituting the transverse hoop elements of the structure. These sections are generaly made of metal, steel or aluminium alloy, and a seal may be interposed between a plate and a section or between a plate and each of the superposed sections.
In such a structure the two upper and lower transverse sections constituting each hoop element are rendered fast with each other, at each end, by means of a locking screw which is screwed in an open tubular rib provided on the inner face of the upper section. This open tubular rib presents an outer diameter substantially equal to the distance separating two ribs provided on the inner face of the lower section and betwen which is engaged the open tubular rib fast with the upper section. Consequently, the engagement of the locking screw in the open tubular rib provokes to some extent a diametrical expansion of the latter which is applied firmly against the two ribs fast with the lower section. Such a structure consequently presents the drawback of not ensuring a good seal, as the two sections of each hoop element are connected to each other by an effort exerted parallel to the plate of which the edge is housed between the two sections.
The above drawback is also met with at the joint between the connecting crosspieces perpendicular to the hoop elements and these hoop elements, when these crosspieces are present in the structure. The connection between the crosspieces and the hoop elements is generally not very water-tight.